Worms farms are pretty simple pieces of equipment. You have a few layers of trays where you put your veggie scraps and worms, separated by a perforated mesh that the worms can move through. The top and bottom are sealed to keep the worms in and insects out, while collecting (very fertile) liquid at the very bottom. You fill the bottom tray with scraps, then move on to the next tray up. When the worms are done with the bottom tray, you empty it into your garden as wonderful compost and soil improver, move that tray to the top and continue.
Most worm farms are made out of molded plastic. The structures are very simple. The material is cheap. The Chinese manufacturing miracle should be able to churn these things almost for free.
Thing is, the cheapest I've been able to find is $65 from The Watershed, run by Marrickville and Sydney councils. At Bunnings the cheapest is about $80, yet you can buy a Mitre Saw, full of complex machinery and electronics, for $30. Someone, somewhere is making a lot of profit on these worm farms.
If anyone out there has any expertise in plastics moulding and mass manufacturing, there's a lot of money to be made undercutting these price gougers.
One option is to make your own, but it shouldn't be so hard!